This is a 3D printed housing for the SmartThings Motion Sensor (2015) that takes 2 AAA batteries, instead of the single CR2450 button cell battery of the original case. The 2 AAA batteries combined should provide a significantly increased energy capacity of over 2000 mAh, compared to the ~600 mAh of the button cells, and for only a fraction of the price.
I was sick and tired of replacing the costly CR2450 batteries that these ST motion sensors use. The good brand ones cost around €1-2/each and last for about 6 months if you're lucky, while the cheap ones from Aliexpress can be had for as low as 30 cents/each, but they are typically crappy and die in a only few months. On the contrary, AAA alkaline batteries are much cheaper (eg. Ikea sells a pack of 10 for €1.79 with a capacity of 1100 mAh) and 2 of them wired in series provide the same voltage than a single CR2450 and more than 3x the capacity. So removing the need to buy button cells to keep these sensors running is clearly a win.
This printable case is of the exact same width and height of the original, and only a few millimeters deeper. Note that it is not a full replacement for the original case but instead it only replaces the white enclosure, and it's meant to be fitted with the original back plate. The wall mounting plate can also be used with this new case.
Note: these ST motion sensors are crap anyway. They are totally energy inefficient, give false positives from time to time and often they just go bust and start reporting motion even within a sealed box. Don't buy them, there are much better options out there, but if you already have them then this printable case can ease the pain a little bit. I just wouldn't rely on them for anything critical.
XYZprinting da Vinci 1.0 (heavily modded)
The battery compartment has a length of 44.9 mm, whereas AAA batteries are typically 44.5 mm long. The 0.4 mm clearance was just about right for my printer, but YMMV depending on your printer's tolerance and accuracy.
The idea was to use paper clips cut to the right size to serve as contact pads. You can see this done in the attached pictures. These pieces of paper clip can be easily glued to the case with cyanoacrylate (superglue).
Tip: if the batteries fit a bit too loose, try bending the contact pins in one of the sides a little bit, kinda looking like a lightly flexed leg. Another approach is to use a more dense glue, like hot melt silicone glue sticks, to pad the contact pins just enough for a tighter fitting.
Soldering the wires to the motion sensor's circuit is trivial (and you'll probably do a much better job than I did :). Just watch the polarity! The contact pad on the bottom is the negative, and the raised one on the side is the positive.